Under the restriction scheme, only cars with license-plate numbers ending in one of two given digits will not be allowed on the affected roads on certain days.

Similar traffic-control systems have been implemented in other Chinese cities, most notably Beijing, where such a scheme was put in place in 2007. Nanchang, Lanzhou, Changchun, Hangzhou, and Guiyang have all followed suit. But such restrictions have been criticized both by car owners and transport-planning experts.

Road traffic has actually increased since the limits have been put into place in Lanzhou, said a Lanzhou CPPCC councilmember, as wealthy car owners simply purchase a second car to skirt the regulation. However, a 2011 study on Beijing's driving restrictions indicates that while the effect on traffic flow might be negligible, air pollution in the city falls drastically on days restrictions are in place.

In Chengdu, where the municipal government announced this year that improving traffic flow will take priority in its development plan, the limitations will be in place on the Second Ring Road Monday to Friday from 7:30 a.m. to 10 p.m. and only during rush morning and evening rush hours on weekdays on Jiefang Lu, Shudu Dadao East and West Sections, Hongxing Lu North and South Sections, Chuanzang Lu, and Laochengguan Lu. Other roads will be unaffected.

The Chengdu Transit Authority estimates that the restrictions will affect between 14 and 21.95 percent of motor vehicles between Monday and Friday.

Public-transportation and commercial vehicles will not be affected by the restrictions.

Netizens criticized the restrictions as too complicated and expressed dissatisfaction with transportation in the city.

According to a January 2012 West China City Daily report, there are more 40,000 people per square kilometer in Chengdu and more than 2 million cars on Chengdu's roads, more than in any other Chinese city apart from Beijing and Chongqing. And car ownership rates continue to rise rapidly.

Chengdu's urban roadways are built to a maximum capacity of 550,000 vehicles. In January 2012, the daily traffic rate in the city center had already reached 450,000 vehicles. Car ownership in the urban area already exceeded 990,000 vehicles.

Across the mainland, seven cities are home to more than 2 million cars, and 23 have more than 1 million on their roads.

In 2011, 22.69 million more people became drivers, among whom 11.09 percent had less than one year of driving experience.

QQ's Chengdu portal has set up a special section dedicated exclusively to information-dissemination, news, and discussion of Chengdu's driving restrictions here.

In the meantime, it was announced that the long-awaited Metro Line 2 is expected to begin operating in late September of this year, increasing the city's daily public transportation capacity by 500,000 passengers. The current capacity is around 4.05 million.